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MDL-25500 Lock: Unit tests have found that MySQL locks are broken

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Removing the MySQL lock factory, the only safe way to use this MySQL API
would be to open a new DB connection for every lock. Record locking is a decent
fallback.
This commit is contained in:
Damyon Wiese 2014-01-29 11:52:51 +08:00
parent fefcd9abab
commit 37b2c56569
1 changed files with 0 additions and 157 deletions
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157
lib/classes/lock/mysql_lock_factory.php
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@ -1,157 +0,0 @@
<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* MySQL GET_LOCK locking factory.
*
* @package core
* @category lock
* @copyright Damyon Wiese 2013
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
namespace core\lock;
defined('MOODLE_INTERNAL') || die();
/**
* MySQL GET_LOCK locking factory.
*
* Use MySQL GET_LOCK functions to support locking. Supports auto-release and timeouts and should be fairly quick.
*
* @package core
* @category lock
* @copyright Damyon Wiese 2013
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class mysql_lock_factory implements lock_factory {
/** @var \moodle_database $db Hold a reference to the global $DB */
protected $db;
/** @var string $type Used to prefix lock keys */
protected $type;
/** @var array $openlocks - List of held locks - used by auto-release */
protected $openlocks = array();
/**
* Is available.
* @return boolean - True if this lock type is available in this environment.
*/
public function is_available() {
return $this->db->get_dbfamily() === 'mysql';
}
/**
* Almighty constructor.
* @param string $type - Used to prefix lock keys.
*/
public function __construct($type) {
global $DB;
$this->type = $type;
// Save a reference to the global $DB so it will not be released while we still have open locks.
$this->db = $DB;
\core_shutdown_manager::register_function(array($this, 'auto_release'));
}
/**
* Return information about the blocking behaviour of the lock type on this platform.
* @return boolean - Defer to the DB driver.
*/
public function supports_timeout() {
return true;
}
/**
* Will this lock type will be automatically released when a process ends.
*
* @return boolean - Defer to the DB driver.
*/
public function supports_auto_release() {
return true;
}
/**
* Multiple locks for the same resource can be held by a single process.
* @return boolean - Defer to the DB driver.
*/
public function supports_recursion() {
return true;
}
/**
* Create and get a lock
* @param string $resource - The identifier for the lock. Should use frankenstyle prefix.
* @param int $timeout - The number of seconds to wait for a lock before giving up.
* @param int $maxlifetime - Unused by this lock type.
* @return boolean - true if a lock was obtained.
*/
public function get_lock($resource, $timeout, $maxlifetime = 86400) {
$params = array(
'key' => $resource,
'timeout' => $timeout
);
$result = $this->db->get_record_sql('SELECT GET_LOCK(:key, :timeout) AS locked',
$params);
$locked = (bool)($result->locked);
if ($locked) {
$this->openlocks[$resource] = 1;
return new lock($resource, $this);
}
return false;
}
/**
* Release a lock that was previously obtained with @lock.
* @param lock $lock - a lock obtained from this factory.
* @return boolean - true if the lock is no longer held (including if it was never held).
*/
public function release_lock(lock $lock) {
$result = $this->db->get_record_sql('SELECT RELEASE_LOCK(:key) AS unlocked', array('key' => $lock->get_key()));
$result = (bool)$result->unlocked;
if ($result) {
unset($this->openlocks[$lock->get_key()]);
}
return $result;
}
/**
* Extend a lock that was previously obtained with @lock.
* @param lock $lock - a lock obtained from this factory.
* @param int $maxlifetime - the new lifetime for the lock (in seconds).
* @return boolean - true if the lock was extended.
*/
public function extend_lock(lock $lock, $maxlifetime = 86400) {
// Not supported by this factory.
return false;
}
/**
* Auto release any open locks on shutdown.
* This is required, because we may be using persistent DB connections.
*/
public function auto_release() {
// Called from the shutdown handler. Must release all open locks.
foreach ($this->openlocks as $key => $unused) {
$lock = new lock($key, $this);
$this->release_lock($lock);
}
}
}